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authorJosé Pekkarinen <jose.pekkarinen@nokia.com>2016-04-11 10:41:07 +0300
committerJosé Pekkarinen <jose.pekkarinen@nokia.com>2016-04-13 08:17:18 +0300
commite09b41010ba33a20a87472ee821fa407a5b8da36 (patch)
treed10dc367189862e7ca5c592f033dc3726e1df4e3 /kernel/drivers/i2c/busses/i2c-sirf.c
parentf93b97fd65072de626c074dbe099a1fff05ce060 (diff)
These changes are the raw update to linux-4.4.6-rt14. Kernel sources
are taken from kernel.org, and rt patch from the rt wiki download page. During the rebasing, the following patch collided: Force tick interrupt and get rid of softirq magic(I70131fb85). Collisions have been removed because its logic was found on the source already. Change-Id: I7f57a4081d9deaa0d9ccfc41a6c8daccdee3b769 Signed-off-by: José Pekkarinen <jose.pekkarinen@nokia.com>
Diffstat (limited to 'kernel/drivers/i2c/busses/i2c-sirf.c')
-rw-r--r--kernel/drivers/i2c/busses/i2c-sirf.c26
1 files changed, 22 insertions, 4 deletions
diff --git a/kernel/drivers/i2c/busses/i2c-sirf.c b/kernel/drivers/i2c/busses/i2c-sirf.c
index 1092d4eee..13e51ef6a 100644
--- a/kernel/drivers/i2c/busses/i2c-sirf.c
+++ b/kernel/drivers/i2c/busses/i2c-sirf.c
@@ -358,11 +358,29 @@ static int i2c_sirfsoc_probe(struct platform_device *pdev)
if (err < 0)
bitrate = SIRFSOC_I2C_DEFAULT_SPEED;
- if (bitrate < 100000)
- regval =
- (2 * ctrl_speed) / (bitrate * 11);
- else
+ /*
+ * Due to some hardware design issues, we need to tune the formula.
+ * Since i2c is open drain interface that allows the slave to
+ * stall the transaction by holding the SCL line at '0', the RTL
+ * implementation is waiting for SCL feedback from the pin after
+ * setting it to High-Z ('1'). This wait adds to the high-time
+ * interval counter few cycles of the input synchronization
+ * (depending on the SCL_FILTER_REG field), and also the time it
+ * takes for the board pull-up resistor to rise the SCL line.
+ * For slow SCL settings these additions are negligible,
+ * but they start to affect the speed when clock is set to faster
+ * frequencies.
+ * Through the actual tests, use the different user_div value(which
+ * in the divider formular 'Fio / (Fi2c * user_div)') to adapt
+ * the different ranges of i2c bus clock frequency, to make the SCL
+ * more accurate.
+ */
+ if (bitrate <= 30000)
regval = ctrl_speed / (bitrate * 5);
+ else if (bitrate > 30000 && bitrate <= 280000)
+ regval = (2 * ctrl_speed) / (bitrate * 11);
+ else
+ regval = ctrl_speed / (bitrate * 6);
writel(regval, siic->base + SIRFSOC_I2C_CLK_CTRL);
if (regval > 0xFF)